U.S. patent number 6,567,053 [Application Number 09/781,720] was granted by the patent office on 2003-05-20 for magnetic dipole antenna structure and method.
Invention is credited to Laurent Desclos, Sebastian Rowson, Eli Yablonovitch.
United States Patent |
6,567,053 |
Yablonovitch , et
al. |
May 20, 2003 |
Magnetic dipole antenna structure and method
Abstract
The spiral sheet antenna allows a small efficient antenna
structure that is much smaller than the electromagnetic wavelength.
It achieves the small size by introducing a high effective
dielectric constant through geometry rather than through a special
high dielectric constant material. It typically includes a
rectangular cylinder-like shape, with a seam. The edges of the seam
can overlap to make a high capacitance, or they can make a high
capacitance by simply having the edges of the seam very close to
each other. The high capacitance serves the same role as a high
dielectric constant material in a conventional compact antenna.
Inventors: |
Yablonovitch; Eli (Malibu,
CA), Desclos; Laurent (Los Angeles, CA), Rowson;
Sebastian (Santa Monica, CA) |
Family
ID: |
25123694 |
Appl.
No.: |
09/781,720 |
Filed: |
February 12, 2001 |
Current U.S.
Class: |
343/767;
343/700MS; 343/770; 343/789; 343/895 |
Current CPC
Class: |
H01Q
13/12 (20130101); H01Q 13/22 (20130101); H01Q
5/35 (20150115); H01Q 5/378 (20150115) |
Current International
Class: |
H01Q
13/10 (20060101); H01Q 13/12 (20060101); H01Q
13/22 (20060101); H01Q 13/20 (20060101); H01Q
5/00 (20060101); H01Q 013/10 () |
Field of
Search: |
;343/7MS,702,767,770,789,795,895 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Wheeler, Harold A., Small Antennas, IEEE Transactions on Antennas
and Propagation. Jul. 1975. .
Sievenpiper, D.; Zhang, L.; Broas, Romulo F. Jimenez; Alexopolous,
Nicholas G; Yablonovitch, Eli. High-Impedance Electromagnetic
Surfaces With a Forbidden Frequency Band--IEEE Transactions on
Microwave Theory and Techniques, vol. 47, No. 11, Nov.,
1999..
|
Primary Examiner: Phan; Tho
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application relates to concurrently filed, co-pending
application U.S. patent application Ser. No. 09/781,779, entitled
"Spiral Sheet Antenna Structure and Method" by Eli Yablonovitch et
al., owned by the assignee of this application and incorporated
herein by reference, filed on Feb. 12, 2001.
This application relates to concurrently filed, co-pending
application U.S. patent application Ser. No. 09/781,780, entitled
"Shielded Spiral Sheet Antenna Structure and Method" by Eli
Yablonovitch et al., owned by the assignee of this application and
incorporated herein by reference, filed on Feb. 12, 2001.
This application relates to concurrently filed, co-pending
application U.S. patent application Ser. No. 09/781,723, entitled
"Internal Circuit Board in an Antenna Structure and Method Thereof"
by Eli Yablonovitch et al., owned by the assignee of this
application and incorporated herein by reference, filed on Feb. 12,
2001.
Claims
We claim:
1. An antenna, comprising: a metallic structure having a first hole
at the front opening and a second hole at the rear opening; and at
least one seam connecting between the first hole at the front
opening and the second hole at the rear opening, wherein the at
least one seam comprises a capacitive structure of a spiral sheet
type, the at least one seam being constructed between a top plate
and a middle plate, the top plate overlapping with the middle
plate, the top plate having a left edge connected to the metallic
structure, the middle plate having a right edge connected to the
metallic structure.
2. The antenna of claim 1, wherein the at least one seam comprises
a capacitive structure.
3. The antenna of claim 1, further comprising a pair of wires
coupled to the antenna, the pair of wires providing energy to the
antenna.
4. The antenna of claim 1, further comprising a wire and a ground,
the wire and the ground coupled to the antenna for providing energy
to the antenna.
5. The antenna of claim 1, wherein an electrical length of the
antenna is less than one-quarter wavelength.
6. The antenna of claim 1, wherein the first and second holes are
on the same side of the metallic structure.
7. The antenna of claim 1, wherein the position of the first and
second holes are facing in the same direction.
8. An antenna, comprising: a metallic structure having a first hole
at the front opening and a second hole at the rear opening; and at
least one seam connecting between the first hole at the front
opening and the second hole at the rear opening, wherein the at
least one seam comprises a capacitive structure of a slot type, the
at least one seam being constructed in a gap between a top left
plate and a top right plate, the top left plate having a left edge
connected to the metallic structure, the top right plate having a
right edge connected to the metallic structure.
9. The antenna of claim 8, wherein the at least one seam comprises
a capacitive structure.
10. The antenna of claim 8, further comprising a pair of wires
coupled to the antenna, the pair of wires providing energy to the
antenna.
11. The antenna of claim 8, further comprising a wire and a ground,
the wire and the ground coupled to the antenna for providing energy
to the antenna.
12. The antenna of claim 8, wherein an electrical length of the
antenna is less than one-quarter wavelength.
13. The antenna of claim 8, wherein the first and second holes are
on the same side of the metallic structure.
14. The antenna of claim 8, wherein the position of the first and
second holes are facing in the same direction.
15. An antenna, comprising: a metallic structure having a first
hole at the front opening and a second hole at the rear opening;
and at least one seam connecting between the first hole at the
front opening and the second hole at the rear opening, wherein the
at least one seam comprises a capacitive structure of a double
parallel plate type, a top left plate having a left edge and a
right edge, a top right plate having a left edge and a right edge,
the at least one seam being constructed between a gap on the right
edge of the top left plate and on the left edge of a top right
plte, the top left plate overlapping with a middle plate, the top
right plate overlapping with the middle plate, the top having plate
having the left edge connected to the metallic structure, the top
right plate having the right edge connected to the metallic
structure.
16. The antenna of claim 15, wherein the at least one seam
comprises a capacitive structure.
17. The antenna of claim 15, further comprising a pair of wires
coupled to the antenna, the pair of wires providing energy to the
antenna.
18. The antenna of claim 15, further comprising a wire and a
ground, the wire and the ground coupled to the antenna for
providing energy to the antenna.
19. The antenna of claim 15, wherein an electrical length of the
antenna is less than one-quarter wavelength.
20. The antenna of claim 15, wherein the first and second holes are
on the same side of the metallic structure.
21. The antenna of claim 15, wherein the position of the first and
second holes are facing in the same direction.
22. An antenna comprising: a metallic enclosure with a plurality of
openings or holes, each opening of hole corresponding to a
different frequency band; and one or more capacitive seams
connecting the openings together, the capacitive seams including
slots in the metal or allow for overlap of metal at the capacitive
seam, to provide more capacitance, wherein the at least one or more
seams comprises a capacitive structure of a spiral sheet type, the
at least one seam being constructed between a top plate and a
middle plate, the top plate overlapping with the middle plate, the
top plate having a left edge connected to the metallic structure,
the middle plate having a right edge connected to the metallic
structure.
23. The antenna of claim 22, wherein the one or more capacitive
seams comprises a spiral sheet type, a slot type, or a double plate
parallel type.
24. An antenna comprising: a metallic enclosure with a plurality of
openings or holes, each opening of hole corresponding to a
different frequency band; and one or more capacitive seams
connecting the openings together, the capacitive seams including
slots in the metal or allow for overlap of metal at the capacitive
seam, to provide more capacitance, wherein the one or more seams
comprises a capacitive structure of a slot type, the at least one
seam being constructed in a gap between a top left plate and a top
right plate, the top left plate having a left edge connected to the
metallic structure, the top right plate having a right edge
connected to the metallic structure.
25. The antenna of claim 24, wherein the one or more capacitive
seams comprises a spiral sheet type, a slot type, or a double plate
parallel type.
26. An antenna comprising: a metallic enclosure with a plurality of
openings or holes, each opening of hole corresponding to a
different frequency band; and one or more capacitive seams
connecting the openings together, the capacitive seams including
slots in the metal or allow for overlap of metal at the capacitive
seam, to provide more capacitance, wherein the at least one seam
comprises a capacitive structure of a double parallel plate type, a
top left plate having a left edge and a right edge, a top right
plate having a left edge and a right edge, the at least one seam
being constructed between a gap on the right edge of the top left
plate and on the left edge of a top right plte, the top left plate
overlapping with a middle plate, the top right plate overlapping
with the middle plate, the top having plate having the left edge
connected to the metallic structure, the top right plate having the
right edge connected to the metallic structure.
27. The antenna of claim 26, wherein the one or more capacitive
seams comprises a spiral sheet type, a slot type, or a double plate
parallel type.
Description
BACKGROUND INFORMATION
1. Field of the Invention
The present invention relates generally to the field of wireless
communication, and particularly to the design of an antenna.
2. Description of Related Art
Small antennas are required for portable wireless communications.
To produce a resonant antenna structure at a certain radio
frequency, it is usually necessary for the structure to be of a
size equal to one-half of the electromagnetic wavelength, or for
some designs, one-quarter of the electromagnetic wavelength. This
is usually still too large.
A conventional solution, to reduce the size further., is to reduce
the effective wavelength of the electromagnetic waves, by inserting
a material of a high dielectric constant. Then, the internal
wavelength is reduced by the square root of the dielectric
constant. This requires special high dielectric constant materials
that add cost, weight and cause an efficiency penalty. Accordingly,
the present invention addresses these needs.
SUMMARY OF THE INVENTION
The present invention provides an effective increase in the
dielectric constant purely by geometry, using a spiral sheet
configuration. The dielectric material can have a dielectric
constant >1, or it can simply be air with dielectric constant 1.
Therefore cheaper dielectric materials can be used. Indeed there is
nothing cheaper than air.
An antenna, comprising a first plate and a second plate, the
combination of the first and second plates serving as a capacitive
structure; and a third metallic structure, coupled to the first and
second plates, thereby producing a cylindrical or substantially
cylindrical current distribution, with two openings or holes at
either end of the cylinder-like shape. Although a cylindrical
current distribution is described, other shapes of current
distribution can be practiced provided that the current is
distributed around two openings or holes, that would construct an
antenna without departing from the spirit of the present invention.
In effect, the overlap between the first and second plates, on the
edge of the cylinder, forms a seam between the two holes at the
ends of the cylinder-like structure.
Advantageously, the present invention discloses an antenna
structure that is more compact, reducing the overall size of a
wireless device. The present invention further advantageously
reduces the cost of building an antenna by using air as the
dielectric. .
Other structures and methods are disclosed in the detailed
description below. This summary does not purport to define the
invention. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial diagram illustrating a cross-sectional view
of a spiral sheet antenna for producing a spiral sheet current
distribution in accordance with the present invention. The
overlapping plates 11 and 12 form a seam between the two openings
at the ends.
FIGS. 2A-2B are pictorial diagrams illustrating a perspective view
of two similar antenna structures having different aspect ratio in
length and width, respectively, of a spiral sheet antenna for
producing a spiral sheet current distribution in accordance with
the present invention.
FIG. 3 is a pictorial diagram illustrating a first possible drive
configuration for a spiral sheet antenna in accordance with the
present invention.
FIG. 4 is a pictorial diagram illustrating a second possible drive
configuration for a spiral sheet antenna in accordance with the
present invention.
FIG. 5 is a pictorial diagram illustrating a first embodiment of a
cylinder-like antenna having two holes at the ends, with a seam
between the two holes for producing a circular current distribution
with a double parallel plate in accordance with the present
invention.
FIG. 6 is a pictorial diagram illustrating a perspective view of a
cylinder-like antenna having two holes at the ends, with a seam
between the two holes for producing a circular current distribution
with a double parallel plate in accordance with the present
invention.
FIGS. 7A-7B are pictorial diagrams illustrating a perspective view
and a cross-section view, respectively, of a third drive
configuration of the cylinder-like antenna shown in FIG. 6 for
exciting a circular current distribution with a double parallel
plate seam in accordance with the present invention.
FIG. 8 is a pictorial diagram illustrating a third embodiment of a
magnetic dipole sheet antenna having two holes at the ends, with a
slot seam between the two holes, allowing a circular current
distribution in accordance with the present invention.
FIGS. 9A-9B are pictorial diagrams illustrating a perspective view
and a side cross-section view, respectively, of a first embodiment
of a shielded spiral sheet antenna having two holes at the ends and
an overlapping seam between the holes, providing shielding from
absorbers adjacent to the antenna.
FIGS. 10A-10B are pictorial diagrams illustrating side views of an
operational mathematical technique for determining shielding
effectiveness in a shield spiral sheet antenna in accordance with
the present invention.
FIG. 11 is a pictorial diagram illustrating an operational
procedure for determining the center of a hole in a shielded spiral
sheet antenna in accordance with the present invention.
FIGS. 12A-12B are pictorial diagrams illustrating a second
embodiment of a shielded spiral sheet antenna with overlapping
capacitive seam structure in accordance with the present invention.
FIG. 12B is a side cross-section view showing the path 128-129
followed by magnetic field lines B.
FIG. 13 is a pictorial diagram illustrating a multi-frequency,
multi-tap antenna with spring contacts W1 and W2 in accordance with
the present invention.
FIG. 14 is a pictorial diagram illustrating the placement of
internal circuit boards inside an antenna in accordance with the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)
FIG. 1 is a pictorial diagram illustrating a cross-sectional view
of a spiral sheet antenna 10, resembling a rectangular cylindrical
shape, with two holes at the ends, and a capacitive seam connecting
the two holes, for producing a cylindrical current distribution.
The spiral sheet antenna 10 can constructed with three plates, a
first plate 11, a second plate 12, and a third plate 13. The
variable d 14 represents the spacing between the first plate 11 and
the second plate 12, and the variable t 15 represents the thickness
of all three plates. A vertical connection 16 connects between the
third plate 13 and the first plate 11, while the third plate 13
connects to the second plate 12 via a vertical connection 17. The
length of the third plate 13, between vertical connections 16 and
17 is selected to be less than a quarter wavelength, .lambda./4n,
where n is the square root of the dielectric constant.
The structure of the spiral sheet antenna 10 increases the
effective dielectric constant by a factor of t/d. Effective
increase in capacitance is due to overlapping plates between the
plate 11 and the plate 12. In effect, the spiral antenna 10
produces a large dielectric constant, without the need for a high
dielectric constant material, just from electrode geometry alone,
i.e. .epsilon..sub.relative =t/d. Effectively, treating the spiral
sheet antenna as a patch type antenna, the required length of the
patch then becomes ##EQU1##
where .epsilon..sub.r is the relative dielectric constant of the
capacitor dielectric.
FIG. 2A is a pictorial diagram illustrating a perspective view of a
spiral sheet antenna 20 for producing a cylinder-like current
distribution. The spiral sheet antenna 20 has a first hole 21 and a
second hole 22, at the ends, and a capacitive seam connecting the
two holes. The alternating current (AC) magnetic field vector
B.sup..omega., is shown entering hole 21 and exiting hole 22.
FIG. 2B is a pictorial diagram illustrating a spiral sheet antenna
25 for producing a cylinder-like current distribution with a
different aspect ratio, with a first hole 26 and a second hole 27.
The structure shape in FIG. 2B is the same as the structure shape
in FIG. 2A. However, the aspect ratio, in FIG. 2B, is different
from the aspect ratio in FIG. 2A. The curved vector I represents
the general direction of the AC currents.
The spiral antennas 20 and 25 in FIGS. 2A and 2B operate like a
single-turn solenoids. A single-turn solenoid consists of a
cylinder-like current distribution. A significant portion of the
electromagnetic radiation produced by the spiral antennas 20 and 25
arises from the alternating current (AC) magnetic field vector
B.sup..omega. that enters and exits from the holes at the end of
the single turn solenoid.
Advantageously, the antennas 20 and 25 do not require a high
dielectric constant ceramic to attain a small dimensional size. The
inherent capacitance in the structure of the antennas 20 and 25
allows a low frequency operation according to the formula:
.omega.=1/LC, where .omega. is the frequency in radians/second, L
is the inductance of the single turn solenoid formed by 11, 16, 13,
17 and 12 in FIG. 1., and C is the capacitance from the thin
overlapping region labeled as the thickness d 15, or the spacing
14.
FIG. 3 is a pictorial diagram illustrating a first drive or feed
configuration 30 for a spiral sheet antenna producing a cylindrical
current distribution. The first drive configuration 30 has a first
plate 31, a second plate 32, a third plate 33, a first hole 34, and
a second hole 35. A drive cable 36 attaches and drives the spiral
sheet antenna 20. In this embodiment, the co-axial drive cable 36
matches any desired input impedance. An optional vertical short
circuit wire, 37, can assist in providing an impedance matching
shunt to the spiral sheet antenna 20.
FIG. 4 is a pictorial diagram illustrating a second drive
configuration 40 of a spiral sheet antenna for producing a
rectangular cylinder-like current distribution. The second drive
configuration 40 has a first plate 41, a second plate 42, a third
plate 43, a first hole 44, and a second hole 45 at the rear opening
of the rectangular cylinder. A feed or drive cable 46 attaches and
drives the spiral sheet antenna 20, with an optional impedance
matching vertical shunt wire 47 connecting between the second plate
42 and the third plate 43. Preferably, the material used to
construct an antenna might have a high electrical conductivity,
e.g. copper depending on the required antenna Q-factor.
FIGS. 3 and 4 illustrate two sample drive configurations applied to
the spiral sheet antenna 20, and are not meant to be an exhaustive
listing since many possibilities abound. One of ordinary skill in
the art should recognize that there are numerous other similar,
equivalent, or different drive configurations that can be practiced
without departing from the spirit of the present invention. A
spiral sheet antenna 20 produces an AC magnetic field that radiates
efficiently in a structure that is smaller than ##EQU2##
that is a typical restriction for a patch antenna, where .lambda.
is the electromagnetic wavelength in vacuum, and .epsilon..sub.r is
the microwave refractive index.
The antenna being described here can be regarded as a rectangular
metallic enclosure with two openings, (at the ends of the
rectangle), and a seam connecting the two holes. The seam functions
as a capacitor and can be implemented in several different ways.
First, the seam can be constructed as an overlapping region as
shown in 20. Second, a seam can be constructed as slot between two
metal sheets as shown in 80 where two edges meet. Third, a seam can
be constructed with a slot under which there is an additional metal
sheet underneath as shown in 60.
FIG. 5 is a pictorial diagram 50 illustrating a first embodiment of
a rectangular cylindrical sheet antenna with an opening at each end
of the rectangular cylinder, and with a seam connecting the two
holes at the ends. The seam comprises of a slot over a double
parallel plate. The rectangular cylindrical current distribution
structure 50 has a second plate 52 overlapping with a first plate
51 in two areas on either side of the slot or seam to provide
capacitance. The third plate 53 is far from the first and second
plates 51 and 52, and therefore contributes little to the
capacitance. The rectangular cylindrical current distribution
structure 50 thus yields the benefit of a large dielectric
constant, without the need for a special dielectric material.
However, the capacitance is diminished by a factor 4 due to the two
capacitors in series from the overlap of the first and second
plates 51 and 52,compared to the same two plates in parallel.
FIG. 6 is a pictorial diagram 60, a perspective view illustrating
the second embodiment of a seam configuration in a rectangular
cylindrical sheet antenna. A first hole 61 is positioned in the
front of the pictorial diagram 60, while a second hole 62 is
positioned at the back of the pictorial diagram 60.The rectangular
cylindrical sheet antenna may be driven in a number of different
ways. A possible approach is to place a wire parallel to the long
axis, but off-center to drive currents across the slot. FIG. 7A is
a pictorial diagram 70 illustrating this, the second type of drive
configuration (of the third seam example, illustrated in FIG. 6)
for the rectangular cylindrical sheet antenna. A coaxial feed cable
74 extends and connects through a third plate 73, a second plate
72, and a first plate 71, to an off-center drive wire 75. FIG. 7B
is a pictorial diagram 76 illustrating a side view of this second
type of drive configuration. A drive wire 77 is shown in
cross-section in FIG. 7B.
FIG. 8 is a pictorial diagram 80 illustrating a third embodiment of
a rectangular cylindrical sheet antenna with a slot seam for
producing a magnetic dipole current distribution. The pictorial
diagram 80 will not operate at as low a frequency as the spiral
sheet structure, all other things being equal, since the
capacitance of a slot seam is less than the capacitance of the
over-lapping sheets in the spiral sheet structure.
FIG. 9A is a pictorial diagram illustrating a perspective view, and
FIG. 9B illustrating a side view, of a first embodiment of a
shielded spiral sheet antenna 90 for producing a cylinder-like
current distribution. The structure in the shielded spiral sheet
antenna 90 is similar to the structure in the spiral sheet antenna
20. A first hole 91 is at one end of the rectangle, and a second
hole 92 is at the other end of the rectangle. An over-lapping seam
93, connects the two holes together. In the case of a cellphone the
pair of holes 91 and 92 is positioned to face away from a user's
ear. A base plate 94, of the shielded spiral sheet antenna 90, is
positioned facing the human body, extending 94a beyond the third
plate 13 at one end and extending 94b beyond the third plate 13 at
the other end. The shielded spiral sheet antenna 90 therefore faces
away from the human body. The width of the border w and w'
determines the degree of front-to-back shielding ratio. If
w.apprxeq.t and w'.apprxeq.t, then a shielding ratio of 3 dB or
better can be achieved.
FIGS. 10A and 10B are pictorial diagrams illustrating side views of
a operational mathematical technique for defining a shielded spiral
sheet antenna. To define the shielded spiral sheet antenna 100, two
center points are chosen, a geometrical center point of a top
opening 101 and a geometrical center point of a bottom opening 102.
A path 103, L.sub.s, represents the shortest path between the
geometrical center point of a top opening 101 and the geometrical
center point of a bottom opening 1(12 on the short side. A path
104, L.sub.e, represents the longest path between the geometrical
center point of a top opening 101 and the geometrical center point
of a bottom opening 102 on the longer side. The path 103 is shorter
than the path 104 that faces a user.
The mathematical relationship between the different variables
should be governed by the following inequality, L.sub.s -L.sub.e
>.alpha.t, Eq. (1), in order to provide a good shielding,
front-to-back. A value of .alpha..apprxeq.1 provides some good
degree of shielding.
FIG. 11 is a pictorial diagram 110 illustrating an operational
procedure for determining the center of a hole for the purposes of
our operational mathematical technique for defining a shielded
spiral antenna. The geometrical center of the top and bottom
openings can be defined as a type of geometrical
"center-of-gravity": ##EQU3##
where R.sup..omega. is the set of position vectors at the edges of
the opening, and R.sup..omega..sub.0 is the center-of-gravity
center point that satisfies the Eq. (2).
This equation defines the center point for use in the mathematical
specification in Eq (1). The point around which all the vectors sum
to zero, defines the center of the hole, or opening. The type of
metallic shielding specified FIGS. 9A, 9B, 10A, and 10B, are useful
for shielding cell phone antennas from the user.
FIG. 12A is a pictorial diagram 120 illustrating a perspective view
of a second embodiment of a shielded spiral sheet antenna (with
overlapping capacitive structure). A first hole 124 and a second
hole 125 are positioned to face away from the user. In effect, both
the first and second holes 124 and 125 are facing the front. A seam
126 connects between the first hole 124 and the second hole
125.
FIG. 12B is a pictorial diagram 127 illustrating a side
cross-sectional view of FIG. 12A, with AC magnetic field
illustrated. The structure diagram has two holes for the magnetic
field entering 128 and exiting 129 the antenna. The rectangular
openings shown, may be smaller than the width of the rectangle. A
rectangular container is intended as an illustration. The
rectangular container may be in a shape resembling a cell phone
body instead.
FIG. 13 is a pictorial diagram illustrating a dual frequency,
dual-tap antenna 130 with a first hole 131, a second hole 132, and
a third hole 133. A first seam 135 connects between the first hole
131 and the third hole 133. A second seam 136 connects between the
hole 132 and the hole 133. Spring contacts w.sub.1 and w.sub.2 can
connect to different circuits on a circuit board, such as for
operating with main cell phone bands including Personal
Communication System (PCS) at 1900 MHz, Global Positioning Systems
(GPS) at 1575 MHz, bluetooth, Advanced mobile phone system (amps)
at 850 MHz, and 900 MHz cell phone bands. The spring contacts are
only an example. The concept is to use multiple taps for the
different frequencies that might be needed in a wireless system.
The multi-taps would be derived from a single antenna
structure.
In general, the antenna structure consists of a metallic enclosure,
with holes, or openings. For each independent antenna, or for each
frequency band, an additional hole or opening must be provided on
the metallic enclosure. For the example in FIG. 13, two
frequencies, require 3 holes. Likewise n-frequencies would require
(n+1) holes or openings, connected by n seams. Some of the
n-frequencies might be identical, for the purpose of space or
polarization diversity.
FIG. 14 is a pictorial diagram 140 illustrating the placement of
one or more internal circuit boards 143 inside an antenna. Radio
Frequency Magnetic fields enter a first hole 141 and exit through a
second hole 142. The internal volume in an antenna can be wisely
utilized as not to waste any unused empty space. The extra space
can be filled with one or more active circuit boards 143 for
operation of a cell phone. The internal circuit boards do not
interfere much with the internal AC RF magnetic fields inside the
antenna structure. This allows the antenna volume to be put to good
use in a small volume cell phone.
The above embodiments are only illustrative of the principles of
this invention and are not intended to limit the invention to the
particular embodiments described. For example, the basic concept in
this invention teaches a metallic structure with at least two
holes, and a seam. One of ordinary skill in the art should
recognize that any type of antenna structure, which possesses these
types of characteristics, is within the spirit of the present
invention. Furthermore, although the term "holes" are used, it is
apparent to one of ordinary skill in the art that other similar or
equivalent concepts may be used, such as opening, gaps, spacing,
etc. Accordingly, various modifications, adaptations, and
combinations of various features of the described embodiments can
be practiced without departing from the scope of the invention as
set forth in the appended claims.
* * * * *